Re: [PATCH] reset: allow to pass NULL pointer to reset_control_put()

[Masahiro Yamada]

Hi Arnd,

2016-05-04 20:24 GMT+09:00 Arnd Bergmann <arnd@xxxxxxxx>:
> On Wednesday 04 May 2016 20:17:51 Masahiro Yamada wrote:
>> Currently, reset_control_put() just returns for error pointer,
>> but not for NULL pointer.  This is not reasonable.
>>
>> Passing NULL pointer should be allowed as well to make failure path
>> handling easier.
>>
>> Signed-off-by: Masahiro Yamada <yamada.masahiro@xxxxxxxxxxxxx>
>> ---
>>
>>  drivers/reset/core.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/reset/core.c b/drivers/reset/core.c
>> index 181b05d..7bb16d1 100644
>> --- a/drivers/reset/core.c
>> +++ b/drivers/reset/core.c
>> @@ -288,7 +288,7 @@ EXPORT_SYMBOL_GPL(reset_control_get);
>>
>>  void reset_control_put(struct reset_control *rstc)
>>  {
>> -       if (IS_ERR(rstc))
>> +       if (IS_ERR_OR_NULL(rstc))
>>                 return;
>>
>>         module_put(rstc->rcdev->owner);
>
> Using IS_ERR_OR_NULL() normally indicates that there is something
> wrong with the API, or with the caller.
>
> What exactly is the idea behind treating an error pointer as a valid
> input to reset_control_put() here? Maybe it should just test for
> NULL?
>

I thought about that a bit,
but there might be some (not nice) drivers that rely on the current behavior.
I did not want to break any boards with my patch.

So, should it be

          if (!rstc)
                    return;
or, perhaps

          if (!rstc || WARN_ON_ONCE(IS_ERR(rstc)))
                    return;

?



-- 
Best Regards
Masahiro Yamada